| 1. |
- Arora, Prakhar, 1987, et al.
(författare)
-
Investigating the effect of Fe as a poison for catalytic HDO over sulfided NiMo alumina catalysts
- 2018
-
Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 227, s. 240-251
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of iron (Fe) as poison present in renewable feeds was studied during hydrodeoxygenation (HDO) overmolybdenum based sulfided catalysts. The study was carried out at 6 MPa and 325 °C in batch reaction conditions. Different concentrations of Fe in the feed were tested over MoS2/Al2O3 and NiMoS/Al2O3. A notable drop in activity for the conversion of oxygenates was observed for both catalyst systems with an increased concentration of Fe in the feed. However, the changes in selectivity of products was opposite for unpromoted and Nipromoted catalysts. In the case of the NiMoS catalyst, at higher Fe concentration, the decarbonated product (C17 hydrocarbons) decreased while the direct hydrodeoxygenation product (C18 hydrocarbons)increased. On the contrary, for the base catalyst (MoS2), there was a decrease in the yield of direct hydrodeoxygenation (C18 hydrocarbons) products and an increase in yield of decarbonated products (C17 hydrocarbons). These sulfided catalysts have different sites for these two different reaction routes and they interacted differently with Fe during the deactivation process. With surface deposition of Fe, the ability of these catalysts to create active sites i.e. via sulfur vacancies deteriorated. TEM-EDX results suggested that the effect of Ni as a promoter for the decarbonation route was nullified and a resultant FeMo phase explains the drop in activity and change in selectivity.
|
|
| 2. |
- Arora, Prakhar, 1987, et al.
(författare)
-
Kinetic study of hydrodeoxygenation of stearic acid as model compound for renewable oils
- 2019
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 364, s. 376-389
-
Tidskriftsartikel (refereegranskat)abstract
- The kinetics during hydrodeoxygenation (HDO) of stearic acid (SA) was investigated to explore the fundamental chemistry and the reaction scheme involved for the reaction with a sulfide NiMo/Al2O3catalyst. Intermediates like octadecanal (C18 O) and octadecanol (C18 OH) were used to resolve the reaction scheme and explain the selectivity for the three major reaction routes (decarboxylation, decarbonylation and direct-HDO). Several reaction parameters, like temperature, pressure, feed concentration and batch-reactor stirring rate, were explored for their effect on changes in rate of conversion and selectivity. A weaker dependence on pressure (40–70 bar) and strong dependence on temperature (275–325 °C) was found for the product distribution during HDO of SA. A model based on Langmuir–Hinshelwood type kinetics was developed to correlate the experimental data. The model well predicted trends in variation of selectivities with the reaction conditions, in part by including intermediates like octadecanol and octadecanal and it predicted phenomenon like inhibiting effects of the fatty acid. The proposed kinetic model is expected to be applicable to liquid phase HDO of different renewable feeds containing long chain fatty acids, methyl esters and triglycerides etc.
|
|
| 3. |
- Arora, Prakhar, 1987, et al.
(författare)
-
The role of catalyst poisons during hydrodeoxygenation of renewable oils
- 2021
-
Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 367, s. 28-42
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrodeoxygenation (HDO) activity of NiMo catalysts have been evaluated in the presence of catalyst poisons in bio-based feedstocks. An in-house synthesized NiMo/Al2O3 catalyst was placed in a refinery unit for biofuel production. Iron (Fe), phosphorus (P) and metals were identified as major contaminants. Calcination treatment was explored to recover the activity of spent catalysts. The effect of Fe, K and phospholipid containing P and Na on catalyst deactivation during hydrodeoxygenation of stearic acid was simulated at lab-scale. Fe caused the most deactivation where the highest feed concentration of the Fe compound resulted in 1480 ppm Fe deposited on the catalyst. Elemental distribution along the radial axis of spent catalysts indicated: Fe deposited only to a depth of 100 μm irrespective of concentration while P and Na from phospholipid and K penetrated deeper in catalyst particles with a distribution profile that was found to be concentration dependent.
|
|
| 4. |
- Ojagh, Houman, 1976, et al.
(författare)
-
Hydroconversion of abietic acid into value-added fuel components over sulfided NiMo catalysts with varying support acidity
- 2019
-
Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 190, s. 55-55-66
-
Tidskriftsartikel (refereegranskat)abstract
- The hydroconversion of abietic-type rosin acids, with a tri-ring structure into mono-ring structure hydrocarbons, was investigated. The reactions were performed at 380 °C under 7500 kPa of H2 pressure over sulfided NiMo catalysts supported on alumina, USY-zeolite and mixed alumina/USY-zeolite. The NiMo supported catalysts were characterized using N2-physisorption, ethylamine-temperature programmed desorption (ethylamine-TPD), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and temperature programmedoxidation (TPO). The sulfided NiMo supported on only USY-zeolite showed the highest selectivity towards production of the mono-ring hydrocarbons such as methyl cyclopentane due to the strong Brønsted acid character of USY-zeolite. Whereas, the sulfided NiMo supported on alumina with weaker Brønsted acidity showed strong selectivity towards the di and tri-ring hydrocarbons such as dimethyl tetralins and retene. Moreover, the selectivities towards the mono-ring hydrocarbons over the NiMo catalysts with mixed supports were lower with a higher alumina content. Finally, the results show that the sulfided NiMo catalyst supported on alumina/USY-zeolite support with 50 wt% zeolite achieved a good level of deoxygenation, ring opening and cracking of the rosin acid while avoiding excessive coke formation.
|
|
| 5. |
- Ojagh, Houman, 1976, et al.
(författare)
-
The effect of rosin acid on hydrodeoxygenation of fatty acid
- 2019
-
Ingår i: Journal of Energy Chemistry. - : Elsevier BV. - 2095-4956. ; 28, s. 85-94
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, inhibition of tall oil fatty acid hydrodeoxygenation (HDO) activity due to addition of rosin acid over sulfided NiMo/Al2O3 was investigated. Oleic acid and abietic acid were used as model compounds for fatty acid and rosin acid respectively in tall oil. After completion of each HDO experiment, the NiMo catalysts were recovered and used again under the same conditions. The results showed that the oleic acid HDO activity of sulfided catalysts was inhibited by addition of abietic acid due to competitive adsorption and increased coke deposition. The rate of carbon deposition on the catalysts increased when abietic acid was added to oleic acid feed. Moreover, the coke was in a more advanced form with higher stability for the catalysts exposed to both oleic acid and abietic acid. Furthermore, a clear correlation between the rate of coke formation and concentration of abietic acid was observed.
|
|
| 6. |
- Salam, Muhammad Abdus, 1983, et al.
(författare)
-
Influence of bio-oil phospholipid on the hydrodeoxygenation activity of NiMoS/Al2O3 catalyst
- 2018
-
Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 8:10
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrodeoxygenation (HDO) activity of a typical hydrotreating catalyst, sulfided NiMo/γ-Al2O3for deoxygenation of a fatty acid has been explored in a batch reactor at 54 bar and 320°C in the presence of contaminants, like phospholipids, which are known to be present in renewable feeds. Oleic acid was used for the investigation. Freshly sulfided catalyst showed a high degree of deoxygenation activity; products were predominantly composed of alkanes (C17 and C18). Experiments with a major phospholipid showed that activity for C17 was greatly reduced while activity to C18 was not altered significantly in the studied conditions. Characterization of the spent catalyst revealed the formation of aluminum phosphate (AlPO4), which affects the active phase dispersion, blocks the active sites, and causes pore blockage. In addition, choline, formed from the decomposition of phospholipid, partially contributes to the observed deactivation. Furthermore, a direct correlation was observed in the accumulation of coke on the catalyst and the amount of phospholipid introduced in the feed. We therefore propose that the reason for the increased deactivation is due to the dual effects of an irreversible change in phase to aluminum phosphate and the formation of choline.
|
|
